I punished my son for his fault this morning.But I would rather not________it;after all,he is only 5 years old.
A:to do
B:do
C:to have done
D:have done
科学家将人体细胞中控制合成胰岛素的一段DNA提取出来,转移到大肠杆菌细胞内的DNA分子上,结果该大肠杆菌合成出了人的胰岛素.其原因是( )
地球上动物种类多种多样,目前已知的大约有( )